Ada Crater: Youthful and Enigmatic

This HiRISE image covers the youthful and enigmatic Ada crater and its fresh ejecta situated on the southern bounds of Meridiani Planum. Ada crater has an approximate diameter of 2 kilometers.

Prior to HiRISE targeting, the crater's freshness was suspected from Mars Orbital Camera (MOC) images showing primary structures in the ejecta, from Thermal
Emission Spectrometer (TES) and Thermal Emission Imaging System (THEMIS) mapping.
THEMIS showed that the crater possesses a thermally distinct ejecta blanket, and TES spectral mapping demonstrated that the area surrounding the crater had been extensively swept clean of the surface deposit (possessing a Fe-rich mineral known as hematite) known to drape Meridiani Planum. The HiRISE sub-image shows that the crater has well-developed and sharp crater morphologic features with no discernable superimposed impact craters—a clear testament to the crater's youthfulness. The interior crater morphology is what makes Ada so enigmatic, as it appears that it consists of two craters (i.e., a smaller crater nested in a larger one). Another idea explaining this "nested" crater-in-crater appearance is that the interior ledge may have been bedrock that slid down the crater wall. However, the darker tone of this interior "exposure" does not appear to match the light-toned bedrock exposed in the upper crater wall. This suggests that the crater sampled two distinct rock types from the subsurface. The presence of these two distinct rock types is an important clue with the difference in strength between these two rock types possibly causing the strange appearance of Ada crater. The other enigmatic aspect is the "scalloped" appearance of the wall rock/rim of the crater. This morphology is more pronounced at other craters in Meridiani Planum, such as Victoria Crater (see TRA_000873_1780) indicating that the more pronounced morphology results from erosion and continued downslope movement of material off the crater wall/rim.

Image PSP_001348_1770 was taken by the High Resolution Imaging Science Experiment
(HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 9, 2006.
The complete image is centered at -3.1 degrees latitude, 356.8 degrees East longitude. The range to the target site was 265.9 km (166.2 miles). At this distance the image scale is 26.6 cm/pixel (with 1 x 1 binning) so objects ~80 cm across are resolved. The image shown here [below] has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 3:32 PM and the scene is illuminated from the west
with a solar incidence angle of 56 degrees, thus the sun was about 34
degrees above the horizon.
At a solar longitude of 132.8 degrees, the season on Mars is Northern Summer.

HiRISE Image PSP_001348_1770

Images from the High Resolution Imaging Science Experiment and additional
information about the Mars Reconnaissance Orbiter are available online at:

For information about NASA and agency programs on the Web, visit: http://www.nasa.gov.
NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology
in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission
Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the
project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and
Technology Corporation and is operated by the University of Arizona.

Note

The highest resolution image is provided in the JPEG-2000 (JP2) format.
A JP2 viewer application and browser plug-in may be freely obtained for
Mac OS X and Windows platforms:
ExpressView by LizardTech, a Celartem Technology Inc. company.